Hitherto, there has been known a saturation and contrast adjusting circuit for a color television receiver set, which comprises, as shown in FIG. 1, a contrast adjusting circuit YG connected between a video detector Vd, having an input terminal VIF adapted to receive a video intermediate frequency, and a video amplifier AY, said video detector Vd having a chroma processing circuit CH leading therefrom, which chroma processing circuit CH includes a band pass transformer BPT followed by an ACC amplifier ACC which is in turn connected to a color saturation adjusting circuit SC via gain adjusting circuit CG, so that the gain adjusting circuit CG is connected between the ACC amplifier ACC and the color saturation adjusting circuit SC, whereby the gain of each of the contrast adjusting circuit YG and the gain adjusting circuit CG can be controlled by a controlled adjusting voltage applied through a common manually variable resistor VR generally referred to as a uni-color volume, so that both contrast and the color saturation can be simultaneously adjusted manually.
In FIG. 1, DM is a color demodulating circuit and MTX is a matrix circuit.
In the saturation and contrast adjusting circuit of the type described above, it is required to employ two independent gain control circuits one for each of the contrast adjusting circuit YG and the gain adjusting circuit CG, resulting in the increased cost and also in such a disadvantage that control characteristic curves of said contrast adjusting circuit YG and the gain adjusting circuit CG, included in the color processing circuit, relative to the controlled voltage given by the variable resistor VR do not coincide with each other completely.
The present invention has been developed with a view to eliminate the above described disadvantage inherent in the conventional saturation and contrast adjusting circuit for a color television receiver set and has for its object to provide a saturation and contrast adjusting circuit wherein the chroma processing circuit is led from the contrast adjusting circuit to make it possible to adjust both the saturation and the contrast by the use of a single gain adjusting circuit with control curves of the brightness and saturation contrast adjusting circuit completely coinciding with each other and which is low in cost.
Another object of the present invention is to provide a saturation and contrast adjusting circuit wherein, by maximizing the gain of the gain adjusting circuit of the contrast adjusting circuit during at least the burst period independently of a control signal of the contrast adjusting circuit, the amplitude of a burst signal can be made free from any influence the gain of said gain adjusting circuit may bring about, and which is so designed as to lessen the deterioration of the differential gain characteristic and the differential phase attributable to amplification in the side of the chroma processing circuit.